Gas turbine



NOV. 22, 1949 TA 2,488,783

GAS TURBINE Filed March 12, 1945 mafia i949 umn. STATES PATENT omce "-""I.T1III *T'Cift -JSIZZZZ' 1 My invention relates to a combustion turbine prime mover for aircraft propulsion. An object is to provide means of achieving best performance for the turbine under all operating conditions.

Another object is to provide a means for controlling the relative rotational speeds of the rotors of any aircraft turbine having contra-rotating stages in order that best flow conditions can be approached atentrance to each stage under all operating conditions.

Another object is to provide a means for preheating the turbine blade cooling air in order that the turbine may operate at best eiiiciency allowed by the maximum working temperatures of the turbine blades. Other objects will appear from the description and drawings.

I accomplish the above objects by the means illustrated in the accompanying drawings in which- Figure 1 shows an axial section of the turbine showing its various elements and control system;

Figure 1a is a chordwise section through the rotor blade of the first stage;

Figure zshows a combination of turbine vector diagrams:

Figure 3 shows a cross section of the automatic indicator mechanismfor controlling the R. P. M. of the exit rotor taken in the plane of the paper;

Figure 4 is a fragmentary top view of the automatic indicator mechanism showing its various displacements; and

Figure 5 is fragmentary elevation of the electrical contactor system shown partly in section taken in the plane of the paper-for actuating the controls of the constant speed propeller governor.

It is a feature of this invention that two rotors of a gas turbine are run in opposite directions so as to extract suflicient of the energy of the gas in two stages to make the machine adequately efficient. It is a feature that these stages are coordinated through the control of the automatically controllable propellers and a mechanism responsive to the direction and velocity of the gas leaving the blades of the first stage.

One master propeller has its speed automatically regulated by a governor controlling the propeller pitch. The second propeller has a governor whose pitch is responsive automatically to the gas velocity and direction leaving the first rotor which drives the master propeller. The second rotor drives the other propeller.

Referring to Fig. 1, air enters the axial-flow compressor 2 by the annular entrance 4. The

compressed air leaves the compressor at exit 6 entering the precombustion chamber 8 from which a. portion of the air passes through the burner II! where it burns with the generated fuel entering the burner by a multiplicity of generation tubes I2. The remainder of the air passes through slots H where it mixes with the burned gases in mixing chamber l6. These hot gases are then passed through the air-cooled nozzles It, then through the blades 20 of stage 1, thence through the contra-rotating blades 22 of stage 2 thence through the stator vanes 24, then through heat exchanger 26 (the purpose of which will be explained subsequently), then out exit 28, and finally are passed to the atmosphere around the air-cooled propeller-blade protector muffs 30.

The fuel system supplying fuel to the turbine generation tubes I2 is arranged as follows. A fuel pump 32 pumps fuel from tank 34 to the pilot's throttle control 35 via line 36. The throttle control 35 meters the fuel to the turbine by way of line 31.

gear drive 48 which in turn drives the constant speed propeller 50 by means of shaft 52. An accessory drive gear 54 is provided to drive the oil pump 56 and the constant speed governor 58.

Push-pull cable 60 connects the constant speed governor 58 to the pilot's speed control lever 62.

2nd stage rotor I0 running in a counter direction to 1st stage rotor 40 drives shaft 12 which in turn drives the sun gear 14 of the planetary gear drive 16 which in turn drives the constant speed propeller 18 by means of shaft 80. An accessory drive gear 82 is provided to drive the oil pump 84 and the constant speed governor 86. Push pull cable 88 connects the constant speed governor 86 to the automatic speed control mechanism housed in the control box 90.

This invention discloses a device to automatically control the 2nd stage rotational velocity so as to give best efiiciency of operation for said 2nd stage under the several operatin conditions of the 1st stage and thereby achieve best turbine efficiency.

Referring to Fig. 2, the solid lines represent a vector diagram for the turbine when running at design conditions. ab is the absolute velocity vector leaving nozzles l8. liddingin the blade speed vector he gives the relative velocity vector ac with respect to the lst stage rotor blades 20. Vector cd represents the relative velocity leaving blade 20.

. .r 1 3 When blade speed de=bc is subtracted from cd there results absolute velocity vector ce at an angle a from the axis of rotation. Adding in the blade velocity cf of the 2nd stage contra blades 22 gives the relative entering velocity vector cf at an angle a. from the axis of rotation. Vector jg represents the relative leaving velocity. When blade speed gh=ef is subtracted from jg there results an absolute velocity vector in approaching stator vanes 24. The gases leave the stator vanes 24 in an axial direction giving velocity vector ha Considering the case where the pilot goes to a reduced throttle condition then if no correction has been made as to rotor speeds the propeller governor would allow the rotors to run at their former constant speed conditions and the vector diagram in Fig. 2 would be altered to that shown by the dashed vectors as follows: ab drops in value to lab; ac changes to kc; cd drops to cl; de=lm; ce changes to cm; ef=mn; of changes to on; Io drops to no: op=gh; in changes to up; and finally hi drops to pq. It will be noted that the change in angle of approach to 1st stage blades 20 amounting to ack is practically negligible as compared with the change of angle of approach ion at entrance to the 2nd stage blades 22.

The 1st stage blades 20 would easily handle such a change in angle as aclc but the 2nd stage off-design condition fcn entering blades 22 would be obviously ineflicient and therefore requires a change in vector diagram in order to correct the angle of approach to something nearer the original angle a. The means of accomplishing this is to reduce the blade velocity from the value mn to the value mr, thus resulting in a relative approach velocity or to blades 22 at the required angle a. and giving a change in vector diagram as indicated by the double dashed vectors as follows: no changes to rs; np changes to rt; and finally pq changes to tu. Note that st=mr.

This invention discloses a device to automatically control the 2nd stage rotational velocity mr so as to give best efliciency of operation for any reasonable throttle setting or change in R. P. M. of the first rotor 40.

Fig. 3 shows a cross section of the automatic indicator mechanism, which in a simple way reproduces or simulates the absolute velocity vector in magnitude and direction as it leaves 1st stage rotor blades 20. This mechanism is located between blades 20 and 22 as shown in control box 90 of Fig. 1. The mechanism (Figures 1 and 3) consists of several elements, the main one being a streamlined vane I that indicates the absolute velocity direction leaving blades 20 and which is connected to the centrifugal indicator housing I02 by means of the hollow shaft I04 which is supported by bearings I05. The vane I00 contains a suitable duct I08 to direct a portion of the turbine gases past the small rotor IIO which drives sun gear II2 by means of shaft II 4. Thus, rotor IIO drives the planet gears I I5 around internal gear H8 attached to housing I02 at a rate directly proportional to the absolute velocity of the turbine gases leaving blades 20. The planet gears II6 drive the centrifugal indicator assembly I which is supported on the hollow slotted shaft I22 by bearings I24.

Assembly I20 is composed of lifter type centrifugal weights I26 pinned to clevis support I28 by pins I30 and operating actuator pin I32 by bear-.

ing on bar I34 sliding in slot I35. The actuator pin I32 is limited to a definite displacement by lever I38 attached to case I02 by pin I40 and spring I42. Lever I in turn actuates arm I44,

male member of screw-Jack I55.

the end of which moves in the plane of vane Ill and actuates link I by means of ball-socket joint I52.

Fig. 4, which is a top view of the automatic indicator mechanism of Fig. 3, reveals the action of the mechanism in reproducing the pertinent portions of the vector diagram already mentioned in the explanation of Fig. 2. Thus, at design conditions, the rotor IIO drives the centrifugal lifter weights I25 at, a rate suillcient to give a displacement X of the ball socket joint; I52 at an angular displacement of e from the turbine axis of rotation I53. At the previously mentioned off-design condition, at decreased throttle, the decreased absolute velocity vector cm in Fig. 2 evidences it--,

self on the mechanism by indicating a displacement of magnitude Y at an angular displacement of ,9 from the turbine axis of rotation I53. These displacements are combined to actuate the propeller speed governor so as to achieve the required 2nd stage blade speed vector mr, in order to maintain a constant value for the relative entrance velocity vector angle a. at the approach to blades 22. In Fig. 4, line I54 at an angle a to a plane through the center line of rotation, would be the locus of all positions of ball joint I52 that makes vector mr of Fig. 2 become zero. The actuator link I50 should be of sufllcient length to maintain a substantially perpendicular position with respect to line I53 throughout the operative range in order to prevent secondary deviations. At design condition the ball joint I52 is located at a distance X from line I54 and at an off-design condition is located at a distance 1. These distances correspond respectively to co and mw of Fig. 2 which are respectively proportional to the 2nd stage'blade speed vectors ef and mr at design and oil-design conditions.

Referring to Fig. 5 it will be noted that link I50 is pinned to a double throw electrical contactor I55 mounted so as to freely slide axially in the Micarta support I56 attached to the fe- The screwjack is actuated by an electric gear motor I50 having a pivot mounting I52. The gear motor is of the reversing type connected as shown in Fig. 5 to the two contacts I52 and I54 mounted on Micarta block I55. The screw-Jack I50 is connected through an appropriate linkage system I55 to the push-pull control cable 55 which in turn is attached to the constant speed governor 55 as shown in Fig. 1. Therefore, any deviation in the flow system that will cause ball joint I52 to displace link I50 will cause contactor I55 to make circuit with either contact I52 or I54 and displace the screw-jack I55 to a point where the contactor I55 is no longer moving, then theelectric circuit is broken with either contact I52 or I54, depending on the direction of travel, at which time the second stage constant speed governor 86 is automatically set at the correct R. P. M. to give the required blade speed vector mr in Fig. 2 to obtain the correct relative entering angle a to blades 22.

Each rotor blade is hollow and has in itssurface one or more slots 51 as shown in Figure la through which air from 25 is passed into the turbine passage. However in the vector diagram of Fig. 2 the rotor and stator blades which are hollow have been shown solid for diagrammatic convenience. The air in passing out of the slot' over the surface provides a protective layer of relatively cool air between the motive gas and the surfaces or the blades Referring to-Fig. 1, air is bled off at annular port I16 of compressor 2 and transferred by means of the annular duct I12 to the entrance of the annular heat exchanger 26 located in the turbine passage IN. Th cooling air passing through 26 absorbs heat from the exhaust gases so that the cooling air temperature is the maximum allowable to cool the blades. the exchange 26 by means of duct I16 which delivers the air tothe rotors 46 and 16 to be employed in cooling the blades in a similar fashion to that shown in my application S. N. 455,528,

- now abandoned.

It will now be clear that I have provided a simple and compact turbine of light weight and high efficiency.

I have now described suitable embodiments of my invention which are now preferred. It is to be understood however that the invention is not limited to the particular construction illustrated and described and that I intend to claim it broadly as indicated by the scope of the appended claims.

I claim:

1. In comb nation to form a gas turbine. two axial flow rotors having blades adapting them forrotation in opposite directions about a common axis, means mounting said rotors in spaced tandem relation for actuation by a common gas stream to rotate said rotors in opposite directions, an adjustable pitch propeller for each rotor and means operably connecting each propeller to its respective rotor for rotation thereby, and means to adjust the relative pitches of said propellers to adjust the rates of rotation of said rotors relative to each other, the last said means'operating automatically in response to a change the direction of said gas stream relative to said rotor.

' said rotors in opposite directions, an adjustable pitch propeller for each rotor and means operably connecting each propeller to its respective rotor for rotation thereby, and means to adjust the relative pitches of said propellers to adjust the rates of rotation of said rotors relative to each other, the last said means operating automatically in response to a change in the direction of said gas stream.

3. In a combination to form a gas turbine, two rotors having blades adapting them for rotation in opposite directions, means mounting said rotors for actuation by a common gas stream rotating said rotors in opposite directions, an adjustable pitch propeller for each rotor and means The air leaves automatically in response to the direction of the gas flow leaving one rotor.

4. In combination to form a gas turbine, two

rotors having blades adapting them for rotation in opposite directions, means mounting said r0 tors for actuation by a common gas stream ro-' tating said rotors in opposite directions, an adjustable pitch propeller for each rotor and means operably connecting each propeller to its respective rotor for rotation thereby, and means to adjust the relative pitches of said propellers .to adjust the rates of rotation of said rotors relative to each other, the last said means operating automatically in response to the direction and magnitude of the velocity of the gas flow leaving the upstream rotor.

5. In combination, in a gas turbine, a plurality 7 of turbine rotors having blades, two of said rotors operably connecting each propeller to its respective rotor for rotation thereby, and means to ad ust the relative pitches of said propellers to adiust the rates of rotation of said rotors relative to each other, the last said means operating having oppositely directed blades to cause rotation in opposite directions, a shaft for each of said rotors fixed thereto, means for mounting said shafts and rotors for rotation in opposite direction under the motive action of a gas, means to supply a gas fiow through the blades of said rotors to rotate them, an adjustable pitch propeller for each said shaft adapted to be driven by its respective shaft, a governor to regulate the speed of rotation of one of said propellers in a prescribed manner, and means to regulate the pitch of the second said propeller in response to the absolute velocity and direction of the gas flow passing from the first said rotor to the second said rotor whereby to provide a 'proper approach of the gas to said second rotor.

6. In combination, in a gas turbine, a plurality of turbine rotors having blades, two of said rotors having oppositely directed blades to cause rotation in opposite directions, a shaft for each of said two rotors fixed thereto, means for mounting said shafts and rotors for rotation in opposite direction under the motive action of a gas, means to supply a gas fiow through the blades of said rotors to rotate them, an adjustable pitch propeller for each said shaft adapted to be driven by its respective shaft, a governor to regulate the speed of rotation of one of said propellers in a prescribed manner, and means to regulate the pitch of the second said propeller in response to the absolute velocity of the gas flow passing from the first said rotor to the second said rotor whereby to provide a proper approach of the gas to said second rotor.

7. In combination, in a gas turbine, a plurality of turbine rotors having blades, two of said rotors havingappositely directed blades to cause rotation in opposite directions, a shaft for each of said two rotors fixed thereto, means for mounting said shafts and rotors for rotation in opposite direction under the motive action of a gas, means to supply a gas flow through the blades of said rotors to rotate them, and means to govern the relative speeds of said two rotors as a function of the velocity and direction of the gas leaving one of said rotors for fiow to the second rotor, whereby the provide a proper angle of approach of the gas flow to said second rotor.

8. In combination in a gas turbine, two rotors having blades, said rotors being adapted to rotation in opposite directions, means mounting 7 turbine gas stream to adjust the pitch 01' said propeller to coordinate the relative rate of rotation of said rotors.

9. In combination in a gas turbine, two rotors having blades, said rotors being adapted to rotation in opposite directions, means mounting said rotors for actuation by a common gas stream rotating said rotors in opposite directions, an adjustable pitch propeller operably connected to one of said rotors, another power absorbing device operably connected to other said rotor positioned ahead of the first said rotor, and means .responsive to the velocity of the turbine gas stream aft of the rotor coupled to said device to adjust the pitch of said propeller to coordinate the relative rates of rotation of said rotors.

10. In combination in a gas turbine, two rotors having blades, said rotors being mounted for independent rotation by a common gas stream, a power absorbing device operably connected to a said rotor, a means for inducing a flow of air operably connected to another said rotor, and means adiacent a said rotor responsive to a change in the peripheral direction of the said gas stream relative to the last-said rotor to adjust the rate of airflow through said means for inducing a flow to coordinate the relative rate of rotation of said rotors.

11. In combinationin a gas turbine, two rotors having blades, said rotors being mounted for independent rotation by a common gas stream. a heating means having a fuel burner for the introduction of fuel thereinto to heat said stream, a power absorbing device operably connected to a said rotor, a means for inducing a flow of air operably connected'to another said rotor, and means responsive to the rate of flow of the said gas stream between said fuel burner and a said rotor to adjust the rate of airflow through said means for inducing a flow to coordinate the relative rate of rotation of said rotors.

12. In combination in a'gas turbine, .a rotor having blades, means mounting said rotor for actuation by a gas stream, heating means having an inlet to receive said stream therethrough, said heating means being adapted to heat said stream enroute to said rotor, an adjustable pitch propeller operably connected to said rotor, and means responsive to the velocity of the turbine gas stream to adjust the pitch of said propeller, said responsive means being positioned downstream from said inlet ami from said rotor.

13. In combination in a gas turbine, a set of axial flow blades mounted in peripherally spaced relation to direct a gas stream therethrough, a rotor having a set of axial flow blades therein, said rotor being mounted for rotation about an axis by said gas stream downstream from the first said set of blades, a mm for inducing a flow of air operably connected to said rotor to be driven thereby, and means responsive to the rate of flow of said gas stream to adjust the rate of flow of said means for inducing, said responsive means being positioned between said sets of blades.

. EQWARD A. STALKER.

REFERENCES drum The following references are of record in the flle of this patent:

UNITED STATES PATENTS Number 

